1. Field of the Invention
Priority is claimed on Japanese Patent Application No. 2003-379872, filed Nov. 10, 2003, the contents of which are incorporated herein by reference.
The present invention relates to a squib (i.e., an ignition apparatus) that is used in a system that uses an explosive such as, for example, a pretensioner apparatus or an airbag apparatus for an automobile.
1. Description of Related Art
Occupant protection apparatuses such as pretensioner apparatuses and airbag apparatuses that are mounted in automobiles operate by being ignited by a squib (i.e., an ignition apparatus) in which a gas generating agent is contained in an inflator, and high pressure gas that is generated by the combustion thereof is introduced into an airbag or the like.
A squib is constructed such that an igniting element is mounted on a header to which is fixed a connecting terminal in the form of a pin. In addition, an igniting agent in the form of an explosive is inserted under pressure into a cap so as to be in contact with the igniting element. The pin that is fixed to the header is electrically connected with a master control unit.
In recent years, a large number of occupant protection apparatuses such as airbag apparatuses and the like that deploy from a steering wheel, a side portion of a seat, and a side portion of the roof have come to be mounted in vehicles, and, to correspond to this, inventions relating to the use of buses between occupant protection apparatuses have been proposed (for example, Japanese Patent Application Laid-Open (JP-A) Nos. 10-154992 and 2000-124932).
In addition, to match this use of buses, inventions relating to squibs inside which are mounted integrated circuits (IC) for communication and ignition have been proposed (for example, Japanese Patent No. 3294582).
However, in the squib structure disclosed in Japanese Patent No. 3294582, because both the explosive and the IC are present together inside a casing cap, there is a possibility that each one will interfere with the performance of the other.
For example, as far as the explosive is concerned, the promotion of a chemical reaction of the explosive may be hindered by moisture contained in the IC. Moreover, as a result of the IC occupying a portion of the interior of a casing cap, the volume of the explosive that can be pressure inserted therein is reduced, thereby affecting the explosive by limiting the heat and pressure that can be created.
On the other hand, as far as the IC is concerned, the IC is affected by gas discharged from the explosive. Moreover, the IC is also affected, for example, by the fact that the shape of the packaging of the IC has to match the shape of the cap so that the density of the explosive is uniform when the explosive is pressure inserted in the casing cap.
The present invention was conceived in view of the above circumstances, and it is an object thereof to prevent an explosive and an IC from mutually interfering with the performances of each other in a squib that is integrated with an IC for communication and ignition.